Process for producing liquid fuels from gaseous olefins



Patented Mar. 7, 1939 PATENT OFFICE PROCESS FOR PRODUCING LIQUID FUELS FROM GASEOUS OLEFINS Hermann Velde and Heinrich Tramm, Oberhausen-Holten, Germany, assignors to Ruhrchemie Aktiengesellschaft,

Oberhausen-Holten,

Ger-

many, a corporation of Germany Application April 27,

1937, Serial No. 139,336

In Germany May 11, 1936 4 Claims.

The polymerisation of olefins to produce liquid fuels is well known and has been frequently described. It is further known to effect condensation of the olefins with or without the use of catalysts. For converting olefins which are gaseous at ordinary temperature, by the use of high pressures in the neighbourhood of from 50 to 200 atmospheres it has been found that it is not possible to convert the olefins completely. The polymerisation products are more or less afiected by temperature and are readily inclined to deposit or separate out carbon; this causes choking of the apparatus which becomes noticeable particularly when the conversion temperatuie has been raised to such amextent that a conversion of over 50% of the olefins contained in the initial gases is reached. In this connection it may be mentioned that 50% is only an approximate figure. According to the olefin content of the gases to be treated and the nature of the olefins it is possible to arrest the separation of carbon when the temperature is low or even when it is high. It has been found that by taking two steps each of which is by itself effective to produce polymerisation of the olefins but which are particularly effective in combination, the olefins are almost all converted into a valuable liquid fuel, while the separation of carbon is completely avoided.

The first step according to the invention consists of the following:

The polymerisation of the olefins produces a reduction in the volume of the gas to be converted, while polymer benzines are continuously formed. In this way the rate of flow of the gas is reduced and therefore the contact time is increased. If the cross section of the stream is reduced by stages or continuously in accordance with the polymerisation the rate of flow of the gases can be maintained practically constant notwithstanding the polymerisation which takes place- It has been found that by systematically reducing the cross section of the stream the separation of carbon can be reduced so that it is almost imperceptible.

The conversion of the olefins may be carried out in apparatus of-various constructions. The accompanying drawing illustrates diagrammatically 'a plant suitable for the application of the 5 invention.

The gases for polymerisation that contain olefins pass through a pipe I into the compressor 2 wherein they are brought to the pressure necessary for carrying out the polymerisation reaction. From the compressor the gases pass into a pre-heater 3 and thence into the actual reaction furnace 4 which is heated by'the burner 5.. The waste gases pass out of the furnace through the channel 22. The preliminarily heated gases that are under pressure pass through a three- 5 stage set of pipes 6, 'l and 8. The number of pipes decreases in the individual stages. When polymerisation has ceased the reaction gases pass through a reducing valve 9 then through the pipe Ill to the separator ll,-wherein the gase- 10 ous reaction products are separated from the condensible reaction products. The condensible constituents pass through a pipe l2 and a cock l3 into the storage tank I4, while the constituents that remain gaseous are drawn l5 ofi at the upper end of the separator and are drawn oii through a pipe 15 past a cock Hi. The end or remaining gas is carried past a cock I! through the pipe I8 and past the regulating valve I9 to the burner 5. Furthermore, provision is 20 made for feeding the burner wholly or additionally with gases of a different origin. These heating gases may be conveyed to the burner 5 by way of a pipe 20 past the cock 2| and the last section of the pipe IS.

The following are examples of the application of the invention.

The reaction gas is passed into tubular converters consisting of parallel tubes. For example in the first conversion stage 100 parallel tubes 3 are employed, the conversion being so carried out that when using for example a gas of 60% (by volume) olefin content, 50 to 60% of the olefins are converted. Without an interim separation of the benzine the gas is fed to a sec- 35 0nd conversion stage in which instead of 100 tubes there are only 60 to "70 tubes of the same internal diameter. In this part of the apparatus 50 to 60% of the olefins remaining are converted. The remaining gas then passes a third 40 conversion stage in which only 30 to 40 tubes of the same cross section are provided. In this third stage the conversion is carried out almost completely. With other olefin contents of the initial gases, it is essential to employ a larger or smaller number of conversion tubes corresponding to the diflerent contractions in the indi- .vidual conversion stages.

Alternatively the olefins may be fed into a heated annular chamber which is formed by an outer cylindrical tube and an insertion which tapers conically so that the cross section of the stream becomes smaller and smaller continuously in the direction of the flowing gases. Furthermore, parallel tubes'may be employed whose inthe consumption of olefins increases.

ternal diameter is gradually reduced or tubes may be used which have a widening insertion so that annular chambers are formed whose cross section is gradually reduced in the direction of flow of the gases. Other constructions in which the cross section becomes smaller in stages or continuously may be. employed.

The second feature, which has particular importance when the gases are not 100% olefins but contain saturated hydrocarbons or other gases not taking part in the conversion, consists in converting the gases at higher temperatures as It has been found that the conversion temperatures necessary for converting the olefins to a product free from carbon is dependent on the partial pressure of the olefins, which pressure is determined mainly by the relationship between the inert gases present and the'olefins present; in fact the conversion temperaturemust be raised higher and higher as the partial pressure of the olefins decreases. Where the olefin content is the necessary reaction temperature is about 450 to 460 C., it being important to observe that by olefins is meant mainly the hydrocarbons with three or more carbon atoms per molecule, although ethylene is by no means excluded. A gas mixture containing about 40 to 45% of olefins is best converted at about 500 C., while a gas mixture containing about 20 to 25% of olefin is converted advantageously at 525 C. The conversion temperature must, according to the present invention, be raised in accordance with the reduction in the content of olefins.

For gas mixtures containing substances which a do not take part in the conversion and are consequently increased in proportion during the conversion, it has been found particularly advantageous to combine the two steps, namely, the reduction in the cross section of the flow and, at the same time, the increase in temperature during the course of the reaction.

The combined method of operation is more fully explained by means of the following example. The apparatus consisted of a three-stage system of tubes. In the first stage three tubes were employed whose internal diameter was 30 mm. and whose thickness of wall was 12 mm. Through these tubes which were at a temperature of 460 C. was passed a gas mixture with a content of 61% of propylene under a pressure of 100 atmospheres. The length of the tubesheated was 600 mm. and 1600 gm. of olefin containing gases were introduced every hour into each tube. After passing through these tubes the gas mixture entered two parallel tubes of the same dimensions which had been heated to 500 C. The remaining gases were then passed through a single tube which had been heated to 525 C. in accordance with the'reduced content of olefins. The olefins present were converted to the extent of into valuable liquid benzines. It was found that carbon was deposited in scarcely measurable quantities. Furthermore it was found that methane or the like separated off only in such small quantities that it was no longer posslble to determine the exact amount of methane. Such an effective conversion of olefins is practically impossible with the known processes.

We claim:

1. A process for converting gaseous olefins into liquid fuels by the use of high pressures and temperatures without the use of catalysts, consisting in reducing the'cross-sectional area of the stream of gases as polymerisation progresses and increasing the polymerisation temperature also as polymerisation progresses.

2. A process for'converting gaseous olefins into liquid fuels by the use of high pressures and temperatures without the use of catalysts, consisting in reducing the cross-sectional area of the stream of gases as polymerisation progresses. 

